In hydraulic systems, a reservoir of fluid is sometimes placed in hydraulic communication with an area of relatively lower elevation. This may be useful, for example, to lubricate, cool, control, or charge components of a vehicle drive train with oil from a sump that is disposed at a higher elevation than the components to be lubricated or cooled. Configurations with elevated reservoirs, however, may suffer from siphoning or leakage of fluid out of the reservoirs. Among other issues, this can result in reduced fluid levels in the reservoirs, which may be detrimental to system performance. For example, in lubrication systems for vehicle transmissions, excessive siphoning of oil from a main sump may require a delay in starting the vehicle or engaging the transmission until the sump has been adequately primed or may result in increased parasitic loads due to a dry sump being filled with siphoned or leaked oil.
In known systems, loss of fluid from elevated reservoirs is sometimes counteracted by pumps moving fluid actively from lower areas to the reservoirs. Due to unavoidable leakage, however, siphoning may still cause the reservoirs to lose fluid, in aggregate, when the pumps are not active.
For these and other reasons, it may be useful to provide an arrangement to prevent siphoning or leakage of fluid from an elevated reservoir.